Are we mature by 18? - CrowdScience podcast, BBC World Service — Transcript

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1. 0:00What changed when you turned 18?
2. 0:03More responsibilities and like, you know,  just feeling like you're not a kid anymore,
3. 0:08you know, you have like things you have to  pay for and like things you have to like
4. 0:12take care of with the government  and fear of like growing older.
5. 0:18Meet friends Marla, Milou and Clara, who  recently reached the ripe old age of 18.
6. 0:25Very excited because I've been waiting to  turn 18 for a very long time of course.
7. 0:29I could finally like go out and get drinks  and stuff like that so it's very fun.
8. 0:34I've been so excited and it's finally there.
9. 0:37I was excited about being able to show my  ID because now I can get in wherever I want.
10. 0:42Normally when you're 17 and you want to  get a drink you have to like play dumb
11. 0:47and like "oh no I forgot my ID" and  now I'm like I am actually 18. Yeah.
12. 0:53So I feel very proud when I'm buying cigarettes or
13. 0:56drinks like I feel very mature but...  Do you feel mature in any other ways?
14. 1:05Do we? Yeah I don't even  know how to do the laundry,
15. 1:07so like how am I supposed to live by myself?
16. 1:12You're listening to CrowdScience from the  BBC World Service. I'm Caroline Steel and
17. 1:17that was a little insight into how mature  three teenagers from Mexico, England and
18. 1:22the Netherlands feel now that they're 18. I should also say that CrowdScience does
19. 1:27not condone underage drinking or smoking  and neither does Marla's dad Richard,
20. 1:32who also happens to be the producer of this show. Anyway the reason Richard asked his daughter about
21. 1:37entering adulthood is because of a question we're  tackling in this episode from listener Lynda.
22. 1:44Hi, so I'm Lynda. I'm currently living  in the UK. I'm originally from Algeria.
23. 1:51My question for CrowdScience is: 'I'm  wondering why 18 years old is determined
24. 2:00as the age of maturity?" This question has been on
25. 2:04Lynda's mind for a while because when she was  18, her maturity was really put to the test.
26. 2:11I was at University in Algeria and students  used to strike for different reasons and there
27. 2:18is one day where there is a strike, but not  all the students wanted to strike. A few of
28. 2:26them they want to attend the lectures and  there was a student from the committee he
29. 2:34came and he explained the reason why they  are striking and everything. Actually I
30. 2:39was convinced by the explanation. So a few students they were also
31. 2:46convinced so they left the lecture.  A few they were not so they stayed.
32. 2:51And for me I was convinced but at the same time I  wanted to attend the lecture so I think there are
33. 3:00a few people like me. So we were standing there  in the middle and then the professor said,
34. 3:07"Well I'm fine with the people who left, I'm fine  with the who stay here, I think the worst thing in
35. 3:13the life is the people standing the middle". And I was a good student and I had a lot of
36. 3:22respect for the professors, so I was so  ashamed. I said, so it is you always need
37. 3:27to take a decision. And not taking a decision is  very bad. It's worse than making a bad decision.
38. 3:35So it was like the point that I decided in the  future I was taking the decision for things.
39. 3:42Do you think that was a bit of a turning  point? Did you become more decisive after that?
40. 3:46Yeah, so I think we need experience in life to  be able to learn and make decisions and mature.
41. 3:56There is a cultural aspect and this affects  a lot the behaviour of people but I think no
42. 4:05matter where we are I think we have the  same, humans. So same physiology. So I'm
43. 4:10wondering if we are mentally and also physically  mature at 18, especially the brain part of it.
44. 4:23Thanks Lynda. To be honest I think your lecturer  was quite harsh there. That's a difficult decision
45. 4:29to make and I can think of countless times in my  late teenage years where I made categorically the
46. 4:34wrong choice. But was I doomed to get it wrong? Maybe our brains and bodies just aren't ready for
47. 4:41good decision- making at 18. And why is 18 the age of
48. 4:45maturity in most countries anyway? Although  interestingly in Algeria, where Lynda's from,
49. 4:50it's actually 19. But regardless of the number,  with reaching the age of maturity you are legally
50. 4:55considered an adult, which may come with the  right to vote, get married or buy alcohol,
51. 5:00amongst others, but from a science point of  view is 18 really the start of adulthood?
52. 5:07Well the age of maturity being set at  18, as it is in most countries actually,
53. 5:12that decision was made long before we knew  anything about the development of the brain.
54. 5:17This is Sarah-Jayne Blakemore.  Professor of Psychology and
55. 5:21Cognitive Neuroscience at Cambridge University.
56. 5:24She's an expert on how our  brain develops with age,
57. 5:27so I'm hoping she can tell us  when our brains fully mature.
58. 5:31That is a really good question and it sounds  like a question that should have an obvious
59. 5:36answer but unfortunately it doesn't. It's  a very complicated question because we
60. 5:42don't really know what a fully mature brain  looks like. There are two reasons for that.
61. 5:49First of all it's only really in the last 20  years that we have been able to look at the
62. 5:55development of the living human brain using  brain scanning technology like MRI so we're
63. 6:00only really quite recently learning about how  the brain develops throughout childhood and
64. 6:05adolescence and into early adulthood. And the  second reason is that the adult brain is still
65. 6:13changing. So our brains are plastic. That means  they adapt to the environment which allows us to
66. 6:20learn new information and acquire new knowledge.  There is no age limit to that neuroplasticity.
67. 6:28So if I showed you two brain scans you  wouldn't necessarily be able to say you
68. 6:33know that's the brain of a 30-year-old and  that's the brain of a 20-year-old?
69. 6:38I can tell you that that would be at the  moment an impossible task for a human to
70. 6:43do. So if you showed me, even though there is a  difference on average if you scan lots of people
71. 6:48there is a difference between a 20-year-old  brain and a 30-year old brain, on average,
72. 6:54even as someone who scans the brain I wouldn't  be able to tell the difference. Now that's
73. 6:59not to say that at some point we won't be able  to tell the difference but at the moment that is
74. 7:04not possible. That's partly because overall there  is not much difference between a 20-year-old and
75. 7:10a 30-year-old brain. For example they're the same  size, the same volume overall. In fact the human
76. 7:16brain becomes about adult size by about age  eight or nine years, so by about nine years
77. 7:23the brain is adult size and it doesn't change  its overall size or volume very much at all.
78. 7:30What changes is the composition of the  brain. For example, the amount of gray
79. 7:35matter and the amount of white matter,  which undergoes very substantial changes
80. 7:39after age nine right throughout  adolescence and into early adulthood.
81. 7:43So there's not sort of, I don't know,  something special that happens to your
82. 7:47brain when you turn 18 and you're suddenly,  supposedly a complete adult? It's not like,
83. 7:53ah that's the average age that your prefrontal  cortex stops developing, or something like
84. 7:58that? There isn't a sort of neuroscience  reason for 18 to be the age of maturity?
85. 8:04So the brain is still developing at 18 in the  vast majority of young people. Their brains
86. 8:11will still continue to develop in terms of the  internal composition of white matter and gray
87. 8:17matter for example, right throughout  the late teens and into the twenties.
88. 8:22Interestingly we've only known  that the brain develops during
89. 8:27adolescence and into early  adult in the last 20 years.
90. 8:30When I was an undergraduate, 30 years ago,
91. 8:33I was taught that the human brain  stops developing in childhood.
92. 8:37I remember being taught that and I also kept  my undergraduate textbooks and that's exactly
93. 8:40what they say. So interestingly, when the legal  age of adulthood was set at 18 many, many decades
94. 8:48ago that was decades before we knew that the  brain continues to develop after childhood.
95. 8:54So it had that decision about the age of legal  maturity had nothing to do with neuroscience.
96. 9:00So now we do know about the development of  the brain, you know, does the neuroscience
97. 9:06somehow follow the legal decision about the  age of maturity? Not much. In terms of their
98. 9:14prefrontal cortex you mention, that's the  part of the brain that is responsible for
99. 9:18things like decision-making and planning and  stopping yourself doing something inappropriate
100. 9:23or for example illegal, it's also involved in  things like self-awareness and social cognition,
101. 9:30understanding other people's minds, that  region of the brain is one of the latest
102. 9:35regions to mature, continues to develop  right throughout the teens and the twenties.
103. 9:40As do the cognitive functions that rely on  the prefrontal cortex. So there's cognitive
104. 9:46functions I just mentioned like decision-making  and planning and inhibition, self-regulation,
105. 9:51they all continue to develop right throughout  the teens and start to plateau into the twenties.
106. 9:57So for most people those abilities start  to sort of become fully mature in the
107. 10:04early twenties but there's nothing special  that happens at 18 in everyone's brain.
108. 10:10That's so interesting. If, you know, part  of our brain which is responsible for good
109. 10:15decision-making in most people hasn't fully  developed until at least their twenties,
110. 10:20it sort of feels like how can we expect  18-year-olds to be making sensible decisions.
111. 10:26Well, by 18 most people's executive  functions, that's the collective name for
112. 10:33these cognitive processes like decision-making  and planning and and inhibiting inappropriate
113. 10:37responses, most people's executive functions are  doing pretty well in terms of how they perform
114. 10:43on these tasks. So I think we can for most  people expect them to be able to make good
115. 10:49decisions by around 18 but the main point  here is that there are very big individual
116. 10:54differences in that. So some people's  executive functions stop improving in
117. 10:59the mid-teens and other people's continue  to develop until the mid twenties.
118. 11:04So, maybe you feel like listener Lynda and me and  you didn't, don't or won't feel mature at 18. Or
119. 11:11you might have been making your best decisions  at just 15. Our brains are all different which
120. 11:16makes it difficult to come up with laws linked  to maturity. So perhaps it's unsurprising that
121. 11:21different countries have drawn the line at  different ages. And the cultural contrasts
122. 11:26aren't just legal. There are also variations  in the ages adult milestones tend to happen,
123. 11:32like marrying or having children. In Algeria where listener Lynda comes from,
124. 11:37the average age of first marriage is 32. In some  countries, like Liberia, it's as low as 21 and
125. 11:44India sits somewhere in the middle at 28. Maybe  the age we choose to do grown-up things could be
126. 11:51a clue as to when and why we're really mature. To help me find out more I'm joined by Chhavi
127. 11:57Sachdev. She's a Mumbai-based journalist  and friend of CrowdScience - hi Chhavi!
128. 12:01Welcome. Hello Caroline. Thank you  for joining us. Always a pleasure. So,
129. 12:07when are people in India seen as mature enough  to get married and have children? So, this is
130. 12:12a difficult question to answer but legally, like  you were talking about with different countries,
131. 12:18in India until 1978 it used to be that girls  could get married at 14 and boys at 18 and then
132. 12:26less than 50 years ago this was changed. Girls can  get married at 18 now and the boys have to be 21.
133. 12:34So what kind of age do people start  feeling pressure to get married and
134. 12:41or have children? I guess it must vary region  to region but are there any sort of patterns?
135. 12:45So I think traditionally there is a sense that  you have certain stages of life and you have
136. 12:52roles you need to perform. So when you finished  studying the next thing you need to do if you're
137. 12:57a boy is get a job, become stable enough to  support a family and then start that family.
138. 13:03For girls you study and then if you're from a  family or a society that believes your role is
139. 13:09really as a homemaker and the mother of society  so you need to have children, then off you go and
140. 13:17start that phase of your life. If I'm not being too nosy
141. 13:21have you felt these pressures? So I am definitely an exception
142. 13:26and an outlier even in my own extended family, and  that's partly because my parents were exceptions.
143. 13:35Back when I was in school it was a thing that  everybody in my classes was amazed at that my
144. 13:42parents had what we call a love marriage. It  was not an arranged match, they chose each
145. 13:46other. And my mother was over the hill compared  with other people, she was in her twenties. She
146. 13:52got an advanced degree and married for love. She was in her twenties, I love how that's old!
147. 13:59Yeah I don't know if she'd appreciate  my telling everybody who's listening,
148. 14:02but she was 25 and that like  you know her chances were over,
149. 14:05she was on the shelf. But she knew what she  was doing. They also really espoused having
150. 14:12a choice and finding your own life partner.  So while my classmates were introduced to a
151. 14:18lot of people or their marriages were set up for  them, I was exempt. But obviously that's just my
152. 14:23experience and as I've said I'm an exception. I  also spoke to Amrita, who grew up in a smaller,
153. 14:30more conservative town, about her experience. Hi, I'm Amrita. I'm almost 49 years old and I
154. 14:36was 22 when I had my first child. I  turned 20 right after I got married.
155. 14:4218, I think I was in school just about to give  my board exams and after that I joined college.
156. 14:49But I never did get to finish it because I got  married when I was in my second year of college.
157. 14:54So there was a lot of pressure on me to do  the right thing at it, as it was called. So
158. 15:00I did have a choice, but it was not much of  a choice. You know at 18, at even 19 or 20,
159. 15:08I don't think I had the maturity or even the
160. 15:13knowledge or the self-awareness  to take any kind of decision.
161. 15:18I don't know what, you know, reservoirs of  strength I tapped into to bring my kids up,
162. 15:24but I think I was too immature and
163. 15:29I did not have the emotional strength  to be a very levelheaded mother.
164. 15:36I don't think women should have children  before they're 26 years old at least. My
165. 15:42daughter has just crossed 26 and I now feel that,
166. 15:47yes, she's prepared for motherhood, for  marriage, for a complex relationship.
167. 15:54It's interesting that Amrita says she  sees her daughter being mature at 26.
168. 15:58I'm 30 and I still think I'm nowhere near mature
169. 16:02enough to have children. But I guess  it really varies culture to culture.
170. 16:08I agree. And I also spoke to another woman, Manju,
171. 16:11who's from a village four hours away from  Mumbai where I live. She had her first
172. 16:16child even earlier and her concerns  were more about physical maturity.
173. 16:23So I was 17 when I had my first child.
174. 16:27Do you look back and think that  was the right age to have a child?
175. 16:37No, no it wasn't.
176. 16:47She said it would have been better if she  was 23 or 24 when she'd had a child. Why?
177. 16:59Everything was hurting her knees, her  back and it was a lot of pain and trouble.
178. 17:08She says when you're older, like 23, 24,  you finish growing, your bones are stronger,
179. 17:13your body is stronger and then  you have the strength to chase
180. 17:15after your children and when you're that  young at 16, 17, you don't have that.
181. 17:24You’re listening to CrowdScience from the BBC  World Service. I’m Caroline Steel and in this
182. 17:31episode we’re looking into listener Lynda’s  question about when we become mature - and
183. 17:35whether 18, the age of legal adulthood in  most countries, has any scientific basis.
184. 17:41We’ve just heard from Amrita  and Manju in India about their
185. 17:45experience of becoming mothers  for the first time at 22 and 17.
186. 17:49Amrita didn’t feel emotionally mature,  which makes sense - we heard earlier
187. 17:54from neuroscientist Sarah Jane that  some people’s brains aren’t fully
188. 17:58developed well into their twenties.  But what about our physical maturity?
189. 18:03It really depends which kind of maturation,  even which kind of biological maturation.
190. 18:10This is Barry Bogin, leading  biological anthropologist and
191. 18:13author of a book called Patterns of Human Growth.
192. 18:17Well, my special interest is  human physical growth, height,
193. 18:20weight, muscle fat and also reproductive maturity.
194. 18:25All those things are already going  on before we're born. You know,
195. 18:28foetuses are growing and  even maturing in many ways.
196. 18:34For instance, our sexual maturation stops
197. 18:37just about at birth and doesn't  even pick up again until puberty.
198. 18:43On average, about age nine  is when it starts up again
199. 18:48and really gets going at ten, 12 years of age.
200. 18:52If we look at height, girls, young women more or  less finish growing in height by about 17 or 18.
201. 18:59Young men are still growing in  height until 22, 23, 24, even 25.
202. 19:06Yeah, a little bit. Most of it is over.  But, for instance, I have a daughter who's
203. 19:12going to be 20 in a few months. She stopped  growing in height basically by 17. She has
204. 19:19a boyfriend. Every time I see him, he's taller  and he's going to be 20 next birthday as well.
205. 19:26Why is it that it's later for men than women?
206. 19:30Boys and girls do have different patterns of  physical growth and maturation. Boys actually
207. 19:38become, we can say fertile. They could produce  fertile spermatozoa by about age 13 to 14. But
208. 19:48those boys still look like little wimps. No older  woman is going to really be interested in them.
209. 19:54Girls, however, look mature.  They start to look like women
210. 19:59years before they are fertile. And they have  what we call secondary sexual development.
211. 20:04The patterns of fatness. Breasts, for  instance, are already noticeable to
212. 20:10everyone in the social group, but they're  not fertile until about age 18. The age
213. 20:18at first birth of women around the world  and throughout history is about age 19.
214. 20:25Now, I know some 12 year olds give birth because  there's a lot of variation in the rate at which
215. 20:31that tempo of maturity plays out but so few  cases are recorded that, like the UK census,
216. 20:40the United States census doesn't even include  those numbers. There's so few of them.
217. 20:45That's interesting. I think that's a really common
218. 20:47misconception. I think generally people  think once you start having a period,
219. 20:51that means you're fertile, right? No.  Turns out probably not for most people.
220. 20:58So just because we start our periods at  around 13 it doesn’t necessarily mean
221. 21:03we’re reproductively mature. Women  might not be fertile until about 18.
222. 21:09But Amrita and Manju gave birth for the  first time at 22 and 17 respectively,
223. 21:14and both felt too young.
224. 21:17Could we have evolved to reproduce  before we’re truly ready?
225. 21:21Yeah, that's a great question. We human  beings are a complex and wondrous mix
226. 21:28of biological and socio-cultural  factors and you can't separate the two.
227. 21:36Biologically, by 20 a woman should be ready  to have a baby. And it's not a bad time
228. 21:41to have a baby if you want one, because  your body is more or less at its prime.
229. 21:46But if you are not ready socially or culturally or  economically, or have too many emotional concerns,
230. 21:53then it could be a very bad time  for you. And even for the baby.
231. 21:57Mothers who are worried pass on that  worry through stress hormones things
232. 22:03like that to their developing  foetus and to their infants.
233. 22:08You might remember that our listener  Lynda was interested in when we mature
234. 22:11physiologically speaking - culture aside.
235. 22:15But as Barry just said, the two  are inextricably entangled. And
236. 22:19that’s what led us to cultural  anthropologist Bonnie Hewlett.
237. 22:22When researching adolescence, she  lived with Aka hunter-gatherers in
238. 22:25the Central African Republic. They’re an  egalitarian community - they believe all
239. 22:31people are equal regardless of age. So does  maturity look different in their culture?
240. 22:37So when a girl has her first period then she
241. 22:41begins to learn more deeply these  foundational key cultural values.
242. 22:47And it's tied into this biological  development. Once that begins,
243. 22:53she is able to become independent
244. 22:57which is a highly regarded value, sacred value,  this sense of autonomy within the family union.
245. 23:04But she can build her own hut. She can signal that  she's ready to begin intimate relations with boys.
246. 23:12In the Aka society they have a fierce,  almost sacred belief in the autonomy of
247. 23:20the individual. So it's always, always  the individual who chooses you know,
248. 23:26when she wants to build her hut,  when he wants to go on a hunt.
249. 23:30So could a girl have her first period  and then decide, like, you know what,
250. 23:34I'm not going to build my  hut for a couple of years.
251. 23:36I'm good as I am, I don't want things to change.
252. 23:40Yeah. Absolutely. Absolutely. And it may be that  she signals to the boys that she's not interested
253. 23:47or she'll have multiple lovers or she'll,  you know, it's absolutely individual choice.
254. 23:54That's interesting because, you know,  in so many other parts of the world,
255. 23:58it's totally different. It sort of decided, okay,
256. 24:01at 16 you are ready to vote in some places,  say. At 18 you're ready to drink and you're
257. 24:08legally an adult and you're completely,  legally responsible for your decisions.
258. 24:12It's not the person's decision  about their own maturity.
259. 24:16Yeah. No. Absolutely. By 10 the Aka children  can fully take care of themselves. They can
260. 24:24hunt, they can cook, they can make  medicines to cure their illnesses.
261. 24:29In these societies, in this development of  identity and confidence, it begins in infancy,
262. 24:35you know, from the moment the child is born,
263. 24:38there's respect for that child as an  individual. Parents don't tell them no.
264. 24:45They let them play with machetes. They  let them learn how to play around fire.
265. 24:49They're regarded as an independent person that  can make their own choices. This movement toward
266. 24:58identity, toward confidence, toward  maturity, really is set in the time of birth.
267. 25:05Do you think we could benefit from perhaps  having more choice in decisions around maturity?
268. 25:14Again, it's a cultural construct. But  I think as we've seen with the Aka,
269. 25:19there's different ways of becoming and  there's diversity in the experience of
270. 25:25identity formation and the formation  of maturity, whatever that is.
271. 25:30And I think, yeah, if we had a better sense of,
272. 25:34individual growth and development rather  than society wide "this is what you are
273. 25:41when you're 18" or what you should be. I  don't think that's useful in some ways.
274. 25:47Perhaps there is something to be said for being  able to navigate our own path to adulthood.
275. 25:51Because we’re all different, biologically  and culturally. And it’s clear that the
276. 25:56two are inseparable. Aka children sound  worlds more mature at 10 than I was at 18.
277. 26:02Which made me wonder, does the environment  you grow up in change your psychological
278. 26:07maturity? What happens, say, if that  environment is chaotic or unsupported?
279. 26:13Do you grow up faster, or just have to cope  with more stuff with a less mature brain?
280. 26:19Here’s neuroscientist Sarah Jane Blakemore again.
281. 26:22That's a really good question. And both of  those things are probably true. So first of
282. 26:25all we know that the developing brain, so  the brain in childhood and adolescence is
283. 26:30particularly plastic and changeable, which  means that childhood and adolescence is a
284. 26:37sort of sensitive period of brain  development, whereby the brain is
285. 26:40particularly susceptible to being moulded and  shaped by the environment it's growing up in.
286. 26:47And if that environment can be positive, but it  can also be negative and that for sure will affect
287. 26:52the brain the way the brain develops. We know that  from a lot of animal research, but we also know
288. 26:57from recent research on development of the human  brain. But equally the second suggestion is also
289. 27:05right, that being exposed to different pressures  at a young age means that you're having to cope
290. 27:12with lots of different responsibilities when your  brain isn't at a level of maturity that maybe it
291. 27:17should be to cope with those pressures,  and that will affect the way you develop.
292. 27:23So not only does our brain determine  how we behave in our environment,
293. 27:27our environment can actually shape our brain.
294. 27:30Which reminds me of listener Lynda’s defining  experience as a young university student, trying
295. 27:36(and failing) to decide between walking out of a  lecture and striking or staying put and learning.
296. 27:42I wondered what Sarah Jayne made of this story.
297. 27:45It's not a simple decision. You have to be  thinking about, you know, the counterfactuals.
298. 27:50You have to be thinking about the consequences  of your actions. Also the social consequences,
299. 27:55what your peers will think about you.  There may be pressure to follow them.
300. 27:59What the lecturer will think about you. There may  be negative repercussions of making that decision,
301. 28:04other kinds of future repercussions. It's  not a simple decision for actually anyone
302. 28:08to make at any age, but certainly at the  age of 18. I mean, I think, you know,
303. 28:12most of us remember being 18 and would agree that  we were not our fully mature selves at that age.
304. 28:21Lynda I hope that helps you stop beating  yourself up about your adolescent decision
305. 28:24paralysis. But it makes sense that it felt like  a turning point because our brains are plastic,
306. 28:30that moment itself could’ve  contributed to you growing up.
307. 28:34You wanted to know why 18 is  the legal age of maturity.
308. 28:39Well the answer is slightly unsatisfying.  It’s because we decided it is. Science
309. 28:44doesn’t entirely back it up - there is  no overnight transformation on your 18th
310. 28:49birthday. Some of us might have reached  full maturity by then but others may have
311. 28:54a full decade to go. Ideally we’d all have  our own “coming of age” age but that could
312. 29:00make it kinda complicated to decide  who can vote… or run for President.
313. 29:05Thanks so much for getting in touch  Lynda, over to you for the credits.
314. 29:09That's all for this episode  of CrowdScience. If you have a
315. 29:12question you would like the team to look into  please email us at [email protected].
316. 29:22This programme was presented by Caroline Steel and
317. 29:25produced by Richard Walker.  Thanks for listening. Bye.